US6584196B1 - Electronic inductor with transmit signal telephone line driver - Google Patents

Electronic inductor with transmit signal telephone line driver Download PDF

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Publication number
US6584196B1
US6584196B1 US09/312,136 US31213699A US6584196B1 US 6584196 B1 US6584196 B1 US 6584196B1 US 31213699 A US31213699 A US 31213699A US 6584196 B1 US6584196 B1 US 6584196B1
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US
United States
Prior art keywords
telephone line
driving stage
amplifier
signal driving
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US09/312,136
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English (en)
Inventor
Frank Sacca
Raphael Rahamim
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Silicon Laboratories Inc
Original Assignee
Conexant Systems LLC
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Filing date
Publication date
Priority to US09/312,136 priority Critical patent/US6584196B1/en
Application filed by Conexant Systems LLC filed Critical Conexant Systems LLC
Assigned to CONEXANT SYSTEMS, INC. reassignment CONEXANT SYSTEMS, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: RAHAMIM, RAPHAEL, SACCA, FRANK
Assigned to CREDIT SUISSE FIRST BOSTON reassignment CREDIT SUISSE FIRST BOSTON SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CONEXANT SYSTEMS, INC.
Priority to JP2000619188A priority patent/JP2003521841A/ja
Priority to KR1020017014501A priority patent/KR20020019020A/ko
Priority to EP00932199A priority patent/EP1180302A1/en
Priority to CNB008102775A priority patent/CN1157923C/zh
Priority to PCT/US2000/012596 priority patent/WO2000070857A1/en
Priority to TW089109097A priority patent/TW457801B/zh
Assigned to BROOKTREE CORPORATION, CONEXANT SYSTEMS, INC., CONEXANT SYSTEMS WORLDWIDE, INC., BROOKTREE WORLDWIDE SALES CORPORATION reassignment BROOKTREE CORPORATION RELEASE OF SECURITY INTEREST Assignors: CREDIT SUISSE FIRST BOSTON
Priority to US10/600,491 priority patent/US7031462B2/en
Publication of US6584196B1 publication Critical patent/US6584196B1/en
Application granted granted Critical
Assigned to SILICON LABORATORIES INC. reassignment SILICON LABORATORIES INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: PCTEL, INC.
Assigned to PCTEL, INC. reassignment PCTEL, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CONEXANT SYSTEMS, INC.
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/028—Arrangements specific to the transmitter end
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/40—Impedance converters
    • H03H11/42—Gyrators
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/46—One-port networks
    • H03H11/48—One-port networks simulating reactances
    • H03H11/485—Simulating inductances using operational amplifiers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0002—Modulated-carrier systems analog front ends; means for connecting modulators, demodulators or transceivers to a transmission line
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
    • H04M11/06—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/0266—Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/0278—Arrangements for impedance matching

Definitions

  • the present invention relates generally to the field of modem circuits, and more particularly, to an electronic inductor circuit suitable for use in the interface circuit of a high-speed modem.
  • FIG. 1 A prior art electronic inductor circuit 10 , also known as a gyrator, is illustrated in FIG. 1 .
  • An electronic inductor typically consists of a transistor 12 with an emitter resistor Re 14 , further biased by a resistor divider 16 , 18 .
  • the resistor divider 16 , 18 is connected across the rectified voltage Tip and Ring lines, and a large capacitor C 2 is placed between the base of the transistor 12 and ground to block any AC signals on the telephone line from modulating the collector current of the transistor 12 .
  • the electronic inductor is part of the telephone line interface circuit that connects a modem to a telephone line. In this configuration, the electronic inductor determines the DC operating point of the modem or the telephone line without affecting the AC response of the signal transmitted or received.
  • the voltage swing problem is generally solved by using two differential transmit drivers of one-half the desired swing, one single driver with virtually rail-to-rail output swing, or one single driver with power supply greater than 5 volts.
  • Another approach is to drive the base of the transistor 32 in the electronic inductor 30 with the transmit signal 14 , after decoupling the base from the voltage divider 36 , 38 with a suitable resistor 10 , as shown in FIG. 2 .
  • Similar configurations are currently used for telephone answering machines. In the later configuration, however, the non-linear characteristics of the transistor 32 are reflected into the signal transmitted on the line, and the signal lacks the linearity required for high-speed modem applications.
  • the present invention is an electronic inductor circuit in which an operational amplifier drives the base of the electronic inductor transistor, and receives negative feedback from the emitter of the transistor.
  • the transistor and operational amplifier combine to form a voltage-controlled current source (VCCS) with respect to loop current.
  • VCCS voltage-controlled current source
  • a voltage divider connected across the rectified Tip and Ring voltage (or another node of the circuit at an equivalent voltage) provides a DC reference to the positive input of the operational amplifier, so that the line current automatically increases with an increase in line voltage.
  • a capacitor couples the transmit signal driver to the positive input of the operational amplifier.
  • the voltage feedback to the transistor is generally different for the AC and DC signals, which effectively translates to different AC and DC currents through the loop.
  • a second transistor may also be used to provide increased isolation for the AC modem when the device is on-hook.
  • the operational amplifier linearizes the voltage signal at the emitter of the transistor (through the negative feedback input), and causes the line current to swing linearly. Specifically, if the collector voltage is sufficiently above Ve, the harmonic content or distortion of the transmitted signal is at least 80 dB below the fundamental signal level.
  • the present invention may also be configured using a Darlington transistor pair in order to minimize the current required by the operational amplifier driver into the base of the first transistor.
  • FIG. 1 is schematic diagram of a prior-art electronic inductor circuit
  • FIG. 2 is a schematic diagram of a second prior-art electronic inductor circuit
  • FIG. 3 is a schematic diagram of a first embodiment of the present invention.
  • FIG. 4 is a schematic diagram of a second embodiment of the present invention.
  • FIG. 5 is a schematic diagram of a third embodiment of the present invention.
  • FIG. 6 is a schematic diagram of a fourth embodiment of the present invention.
  • a preferred embodiment 50 of the present invention is illustrated in FIG. 3 .
  • An operational amplifier 52 drives the base of the electronic inductor transistor 54 , and receives negative feedback from the emitter of the transistor 54 .
  • the transistor and operational amplifier combine to form a voltage-controlled current source (VCCS) with respect to loop current.
  • VCS voltage-controlled current source
  • a voltage divider 56 , 58 connected across the rectified Tip and Ring voltage (or another node of the circuit at an equivalent voltage) provides DC reference to the positive input of the operational amplifier 52 , so that the line current automatically increases with an increase in line voltage.
  • a capacitor 60 couples the transmit signal driver 62 to the positive input of the operational amplifier 52 .
  • the voltage feedback to the transistor 54 is generally different for the AC and DC signals, which effectively translates to different AC and DC currents through the loop.
  • a second transistor 68 provides increased isolation for the AC modem when the device is on-hook.
  • the network impedance matching block 66 may be designed as either an RC network, or any other suitable circuitry.
  • FIG. 4 A second embodiment 70 of the present invention is illustrated in FIG. 4 .
  • This embodiment is similar to the circuit shown in FIG. 3, except that the second transistor 68 is not used because the network impedance matching block 66 is configured as “virtual impedance.”
  • the circuit however, still provides high performance with lower cost.
  • a third embodiment of the present invention is shown in FIG. 5.
  • a Darlington configuration 54 , 82 is used for the electronic inductor transistor, which provides for multiple feedback points, as selected by closing one of the switches S 1 , S 2 , or S 3 .
  • This configuration provides a convenient platform for intelligent line voltage control, as different feedback points may be selected by external control logic (not shown) in order to properly set the desired DC voltage and current on the line.
  • a fourth embodiment of the present invention is shown in FIG. 6 .
  • the same op-amp/transistor combination may be used to both drive the AC signal and to set the DC loop current.
  • a separate op-amp/transistor combination could be used for the AC signal, and one for the DC current, in order to independently control their respective gains and to improve distortion.
  • the first transistor 100 is used as described above to control the DC line current, determined by the resistors R 1 and R 2 .
  • the second transistor 102 controls the AC line current, which includes the virtual impedance feedback and the transmit signal of the modem. The effects of transistors 100 and 102 are independently summed to the line through current ITR and Itr, respectively.
  • the DC transistor 100 can be biased in a non-linear region at any current without introducing distortion on the AC signal.
  • the AC transistor 102 can be biased with a sufficiently low current to operate in a linear region and provide excellent linearity in the AC signal transmitted to the line.
  • this configuration allows the emitter resistors RE 1 and RE 2 , of transistors 100 and 102 , to set the gains independently for AC and DC, respectively.
  • a hookswitch is generally defined as a switch that physically disconnects the modem circuit components from the telephone line interface, when the modem goes on-hook. Due to the high impedance of the op-amp positive input, resistors R 1 and R 2 in FIG. 6 can be sufficiently large to provide only a negligible loading effect on the telephone line, when the modem is on-hook. Typically, the on-hook resistance requirement can be met worldwide when the sum of R 1 and R 2 is greater than 5 Mohms, which is a realistic resistor value. As a result, the electronic inductor in this configuration can be left permanently connected to the telephone line even when on-hook, provided that the base of the transistor is shorted to ground through a switch to prevent current flow through the transistor.
  • the present circuit configuration has excellent linear characteristics, requires a relatively small output voltage swing in the operational amplifier and in the transmit signal source, and can drive signals on the line as large as 5 volts peak-to-peak with power supplies as low as 1 volt. Because the input impedance of the operational amplifier is large, the transmit signal source does not have to be low-impedance and can be smaller in size and less expensive. Furthermore, this circuit is suitable for line-powered operation as the power supply required to obtain adequate voltage swing on the line can be relatively low.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Networks Using Active Elements (AREA)
  • Amplifiers (AREA)
  • Telephonic Communication Services (AREA)
US09/312,136 1999-05-14 1999-05-14 Electronic inductor with transmit signal telephone line driver Expired - Fee Related US6584196B1 (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
US09/312,136 US6584196B1 (en) 1999-05-14 1999-05-14 Electronic inductor with transmit signal telephone line driver
JP2000619188A JP2003521841A (ja) 1999-05-14 2000-05-09 送信信号電話ラインドライバを有する電子インダクタ
KR1020017014501A KR20020019020A (ko) 1999-05-14 2000-05-09 송신 신호 전화 회선 구동기를 구비한 전자 인덕터
EP00932199A EP1180302A1 (en) 1999-05-14 2000-05-09 Electronic inductor with transmit signal telephone line driver
CNB008102775A CN1157923C (zh) 1999-05-14 2000-05-09 具有发送信号电话线驱动器的电子感应器
PCT/US2000/012596 WO2000070857A1 (en) 1999-05-14 2000-05-09 Electronic inductor with transmit signal telephone line driver
TW089109097A TW457801B (en) 1999-05-14 2000-05-12 Electronic inductor with transmit signal telephone line driver
US10/600,491 US7031462B2 (en) 1999-05-14 2003-06-20 Electronic inductor with transmit signal telephone line driver

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US09/312,136 US6584196B1 (en) 1999-05-14 1999-05-14 Electronic inductor with transmit signal telephone line driver

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US10/600,491 Continuation US7031462B2 (en) 1999-05-14 2003-06-20 Electronic inductor with transmit signal telephone line driver

Publications (1)

Publication Number Publication Date
US6584196B1 true US6584196B1 (en) 2003-06-24

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US09/312,136 Expired - Fee Related US6584196B1 (en) 1999-05-14 1999-05-14 Electronic inductor with transmit signal telephone line driver
US10/600,491 Expired - Fee Related US7031462B2 (en) 1999-05-14 2003-06-20 Electronic inductor with transmit signal telephone line driver

Family Applications After (1)

Application Number Title Priority Date Filing Date
US10/600,491 Expired - Fee Related US7031462B2 (en) 1999-05-14 2003-06-20 Electronic inductor with transmit signal telephone line driver

Country Status (7)

Country Link
US (2) US6584196B1 (ja)
EP (1) EP1180302A1 (ja)
JP (1) JP2003521841A (ja)
KR (1) KR20020019020A (ja)
CN (1) CN1157923C (ja)
TW (1) TW457801B (ja)
WO (1) WO2000070857A1 (ja)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050094802A1 (en) * 2003-10-30 2005-05-05 Tahir Ahmed Direct access arrangement
US20050116773A1 (en) * 2003-05-21 2005-06-02 Laletin William H. Amplifier system with current-mode servo feedback
US20050270107A1 (en) * 2004-06-08 2005-12-08 Devendorf Don C Low distortion amplifier
US20060114001A1 (en) * 2004-11-26 2006-06-01 Chroma Ate Inc. Process and device of high voltage test with detecting function for short/open circuit
US20120314781A1 (en) * 2011-06-10 2012-12-13 Didier Boivin Powerline Control Interface for Frequency and Amplitude Modulation Transmitter
US20140198860A1 (en) * 2013-01-17 2014-07-17 Honda Motor Co., Ltd. Power line carrier communication apparatus

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US4214130A (en) 1978-03-10 1980-07-22 Teltone Corporation Signal coupler
US4437147A (en) 1981-05-19 1984-03-13 Tokyo Shibaura Denki Kabushiki Kaisha Rectifier circuit
GB2117590A (en) 1981-12-18 1983-10-12 Telefongyar Active resistance circuit
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US4528424A (en) 1983-06-24 1985-07-09 International Telephone And Telegraph Corporation Multiparty line adapter with privacy feature controlled by reversal of line polarity at a central power source
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US5764694A (en) 1996-01-25 1998-06-09 Rockwell International Corporation Self-testing and evaluation system
US5799060A (en) 1996-05-16 1998-08-25 Harris Corporation Multi-port caller ID-based telephone ringback test device
US5796815A (en) 1996-12-05 1998-08-18 Advanced Micro Devices, Inc. Communications device with improved ring signal detection
US6081586A (en) * 1998-11-16 2000-06-27 Conexant Systems, Inc. Modem having a programmable universal data access arrangement

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7253680B2 (en) * 2003-05-21 2007-08-07 World Energy Labs (2), Inc. Amplifier system with current-mode servo feedback
US20050116773A1 (en) * 2003-05-21 2005-06-02 Laletin William H. Amplifier system with current-mode servo feedback
US20070257733A1 (en) * 2003-05-21 2007-11-08 Laletin William H Amplifier system with current-mode servo feedback
EP1533985A2 (en) * 2003-10-30 2005-05-25 Mitel Networks Corporation Direct access arrangement
US20050094802A1 (en) * 2003-10-30 2005-05-05 Tahir Ahmed Direct access arrangement
EP1533985A3 (en) * 2003-10-30 2006-02-01 Mitel Networks Corporation Direct access arrangement
US20050270107A1 (en) * 2004-06-08 2005-12-08 Devendorf Don C Low distortion amplifier
US7253689B2 (en) * 2004-06-08 2007-08-07 Telasic Communications, Inc. Low distortion amplifier
US20060114001A1 (en) * 2004-11-26 2006-06-01 Chroma Ate Inc. Process and device of high voltage test with detecting function for short/open circuit
WO2006062941A3 (en) * 2004-12-07 2006-12-07 World Energy Labs 2 Inc Amplifier system with current-mode servo feedback
US20120314781A1 (en) * 2011-06-10 2012-12-13 Didier Boivin Powerline Control Interface for Frequency and Amplitude Modulation Transmitter
US20140198860A1 (en) * 2013-01-17 2014-07-17 Honda Motor Co., Ltd. Power line carrier communication apparatus
US9531438B2 (en) * 2013-01-17 2016-12-27 Rib Laboratory, Inc. Power line carrier communication apparatus

Also Published As

Publication number Publication date
CN1360789A (zh) 2002-07-24
US7031462B2 (en) 2006-04-18
US20040081314A1 (en) 2004-04-29
WO2000070857A1 (en) 2000-11-23
KR20020019020A (ko) 2002-03-09
JP2003521841A (ja) 2003-07-15
TW457801B (en) 2001-10-01
CN1157923C (zh) 2004-07-14
EP1180302A1 (en) 2002-02-20

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